impl Default for RepeatN#139690
Merged
rust-bors[bot] merged 1 commit intorust-lang:mainfrom Apr 18, 2026
Merged
Conversation
rustbot
added
S-waiting-on-review
cuviper
added
the
T-libs-api
tgross35
added
the
needs-fcp
Member
Author
|
r? libs-api |
tgross35
added
the
I-libs-api-nominated
Amanieu
removed
the
I-libs-api-nominated
Member
|
@rfcbot merge libs-api |
Collaborator
|
Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
rust-rfcbot
added
proposed-final-comment-period
rust-rfcbot
added
final-comment-period
Collaborator
|
🔔 This is now entering its final comment period, as per the review above. 🔔 |
Contributor
|
This PR needs to be updated, since it conflicts with the already-merged #130887 |
cuviper
force-pushed
the
iter_repeat_n_default
branch
from
4a9f43f to
ed79787
Compare
Collaborator
|
This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
Member
Author
|
Updated, thanks for pointing out that conflict. |
This creates an empty iterator, like `repeat_n(value, 0)` but without needing any such value at hand. There's precedent in many other iterators that the `Default` is empty, like `slice::Iter`. I found myself wanting this for rayon's `RepeatN` as it lowers to a sequential iterator [here][1]. Since rayon is also optimizing to avoid extra clones, it may end up with parallel splits that have count 0 and no item value. Calling `std::iter::repeat_n(x, 0)` just drops that value, but there's no way to construct the same result without a value yet. This would be straightforward with an empty `Default`. [1]: https://github.com/rayon-rs/rayon/blob/ae07384e3e0b238cea89f0c14891f351c65a5cee/src/iter/repeat.rs#L201-L202
cuviper
force-pushed
the
iter_repeat_n_default
branch
from
ed79787 to
a66b781
Compare
rust-rfcbot
added
finished-final-comment-period
Collaborator
|
The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. |
Member
Author
|
r? libs |
tgross35
approved these changes
Apr 17, 2026
Contributor
rust-bors
Bot
added
the
S-waiting-on-bors
rust-bors
Bot
removed
the
S-waiting-on-review
jhpratt
added a commit
to jhpratt/rust
that referenced
this pull request
Apr 18, 2026
…gross35 `impl Default for RepeatN` This creates an empty iterator, like `repeat_n(value, 0)` but without needing any such value at hand. There's precedent in many other iterators that the `Default` is empty, like `slice::Iter`. I found myself wanting this for rayon's `RepeatN` as it lowers to a sequential iterator [here][1]. Since rayon is also optimizing to avoid extra clones, it may end up with parallel splits that have count 0 and no item value. Calling `std::iter::repeat_n(x, 0)` just drops that value, but there's no way to construct the same result without a value yet. This would be straightforward with an empty `Default`. [1]: https://github.com/rayon-rs/rayon/blob/ae07384e3e0b238cea89f0c14891f351c65a5cee/src/iter/repeat.rs#L201-L202 r? libs-api (insta-stable)
This was referenced Apr 18, 2026
rust-bors Bot
pushed a commit
that referenced
this pull request
Apr 18, 2026
Rollup of 12 pull requests Successful merges: - #147811 (naked functions: respect `function-sections`) - #154935 (Add Sized supertrait for CoerceUnsized and DispatchFromDyn) - #139690 (`impl Default for RepeatN`) - #153511 (`std::any::TypeId`: remove misplaced "and" in `Unique<T>` example) - #154943 (Move recursion out of `MatchPairTree::for_pattern` helpers ) - #155295 (Fix misleading "borrowed data escapes outside of function" diagnostic) - #155427 (ptr: update text in intro text to one in with_addr doc) - #155428 (Fix ICE in borrowck mutability suggestion with multi-byte ref sigil) - #155435 (rustdoc: Fix `redundant_explicit_links` incorrectly firing (or not firing) under certain scenarios) - #155450 (Remove unnecessary safety conditions related to unchecked uint arithmetic) - #155454 (docs: Fix typo in std/src/thready/scoped.rs) - #155467 (`std::error::Request`: clean up documentation)
rust-timer
added a commit
that referenced
this pull request
Apr 18, 2026
Rollup merge of #139690 - cuviper:iter_repeat_n_default, r=tgross35 `impl Default for RepeatN` This creates an empty iterator, like `repeat_n(value, 0)` but without needing any such value at hand. There's precedent in many other iterators that the `Default` is empty, like `slice::Iter`. I found myself wanting this for rayon's `RepeatN` as it lowers to a sequential iterator [here][1]. Since rayon is also optimizing to avoid extra clones, it may end up with parallel splits that have count 0 and no item value. Calling `std::iter::repeat_n(x, 0)` just drops that value, but there's no way to construct the same result without a value yet. This would be straightforward with an empty `Default`. [1]: https://github.com/rayon-rs/rayon/blob/ae07384e3e0b238cea89f0c14891f351c65a5cee/src/iter/repeat.rs#L201-L202 r? libs-api (insta-stable)
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
9 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This creates an empty iterator, like
repeat_n(value, 0)but withoutneeding any such value at hand. There's precedent in many other
iterators that the
Defaultis empty, likeslice::Iter.I found myself wanting this for rayon's
RepeatNas it lowers to asequential iterator here. Since rayon is also optimizing to avoid
extra clones, it may end up with parallel splits that have count 0 and
no item value. Calling
std::iter::repeat_n(x, 0)just drops thatvalue, but there's no way to construct the same result without a value
yet. This would be straightforward with an empty
Default.r? libs-api (insta-stable)